Various processes can be used to make phenol. For example, phenol can be made by the Hock process, which involves alkylation of benzene with propylene to produce cumene, oxidation of the cumene to the corresponding hydroperoxide, and cleavage of the hydroperoxide to produce phenol and acetone.
Phenol can also be made by alkylation of benzene and a C4 alkylating agent to produce sec-butylbenzene, oxidation of the sec-butylbenzene to sec-butylbenzene hydroperoxide, and cleavage of the sec-butylbenzene hydroperoxide to produce phenol and methyl ethyl ketone.
Another process for making phenol involves hydroalkylation of benzene to produce cyclohexylbenzene, oxidation of the cyclohexylbenzene to cyclohexylbenzene hydroperoxide, and cleavage of the cyclohexylbenzene hydroperoxide to produce phenol and cyclohexanone.
However, one or more steps of the processes described above can produce substances that are detrimental to process efficiency. For example, and as illustrated in FIG. 1A (with reference to Example 1), the inventors have discovered that the presence of olefins, such as those produced in the hydroalkylation/alkylation and cleavage steps described above, can interfere with oxidation and result in slower conversion and reduced selectivity to the corresponding hydroperoxide.
Additionally, and as illustrated in FIG. 1B (with reference to Example 2), the inventors have discovered that phenol and phenolics, which may be present in one or more recycle streams of a process for making phenol, can also interfere with oxidation.
That said, many of these substances have boiling points very close to those of cumene, sec-butylbenzene and cyclohexylbenzene, making them difficult to separate by conventional techniques, such as distillation.
As such, what is needed is a process for treating such substances to make them substantially inert relative to, more easily separable from, and/or directly remove them from, phenol production processes.